You might be hearing the term hardfork a lot nowadays in relation with BitCoin. So what is a hardfork. Let Me eXplain.
Currently bitcoin mining happens on a particular algorithm which requires huge computing.So only huge mining pools or companies are able to mine BitCoin. This gives miners a lot of control on the BlockChain. Inorder to avoid that a new algorithm and protocol update is going to happen. This will lead to splitting of block leading to formation of new currency called BitCoin Gold. So when using old protocol and algorithm a block is submitted to network, the nodes running newer version won't accept it. So you won't be able to add block which essentially led to splitting block chain to old and new. BitCoin Gold aims at more decentralization of blockchain.
The SegWit2x hardfork aims at increasing transaction speed of BitCoin transactions. Currently a block size in bitcoin BlockChain is capped at 1MB. So amount of transaction which can go to a block is less result ing in bitcoin transaction taking more time. SegWit2X is planning to increase block size by 2MB thus splitting block chain
Read about adding blocks to blockchain here
https://steemit.com/en-us/@lmx3881/lmx-bitcoin-adding-blocks-to-a-blockchain-20171023t204742968z